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TriTops

Tritops, for measurement of circumferential irregularities on wheels

TriTops in position on rail ready for measurements to be taken. The wheelset does not need to be lifted far off the rail.

RailMeasurement’s TriTops measures irregularities on a railway wheel. The equipment uses different technology from RailMeasurement’s equipment to measure irregularities on rails. TriTops can be taken to site in a handy plastic instrument case and used by one person. It was developed for a major vehicle supplier and is used by them.

Measurements are taken, as with most other equipment for this purpose, by jacking a wheelset off the ground and rotating the wheel by hand while measurements are recorded by the instrument. Typically about 4 wheels can be measured in an hour with two people (one jacks up and turns the wheelset, the other moves the equipment under the train and takes the measurements). Measurements are given at three positions across the wheel tread and at a location from flange-back that can be readily adjusted.

The TriTops software gives the following measurements and shows the following features:

Measurements from 6 successive turns of a wheelset, showing radial displacement against distance around wheel.

Polar plots for an out-of-round wheel (left), before and after reprofiling, and the wheel with a wheelflat, for which the (x,y) measurements are given above. Note that the circumference of 2.6017m (diameter of 0.8281m) is shown for the wheel on the RHS.

One-third octave spectra of the out-of-round wheel shown above. The spectra for the three measuring lines are shown before reprofiling of the wheel (left) and after reprofiling (right). Although irregularities are very much lower after reprofiling than the EN 15610 limit, there is nevertheless a noticeable residual irregularity at the wavelength of the original out-of-round. This is likely to initiate out-of-round on the reprofiled wheel.